CI: Ping actions/checkout@v2, no need to be more specific

Author: akien-mga

.github/workflows/export_html5.yml

@@ -15,7 +15,7 @@ jobs:
       image: barichello/godot-ci:3.3.3
     steps:
       - name: Checkout
-        uses: actions/checkout@v2.3.4
+        uses: actions/checkout@v2
 
       - name: Setup
         run: |